//主函数 main.m

#import <Foundation/Foundation.h>

#import "Singleton.h"

int main(int argc, const char * argv[]) {

    @autoreleasepool {

        Singleton *sing1=

        [Singleton shareInstance];

        Singleton *sing2=[Singleton shareInstance];

        Singleton *sing3=[Singleton new];

        Singleton *sing4=[[Singleton alloc]init];

        Singleton *sing5=[sing4 copy];

        NSLog(@"%@",sing1);

        NSLog(@"%@",sing2);

        NSLog(@"%@",sing3);

        NSLog(@"%@",sing4);

        NSLog(@"%@",sing5);

    }

    return ;

}

//Singleton.h文件

#import <Foundation/Foundation.h>

@interface Singleton : NSObject<NSCopying>

+(Singleton *)shareInstance;

@end

//Singleton.m文件

#import "Singleton.h"

@implementation Singleton

static Singleton *singleton;

//单例方法

+(Singleton *)shareInstance{

    if (singleton==nil) {

        singleton=[[Singleton alloc]init];

    }

    return singleton;

}

//单例方法  初始化

+(instancetype)allocWithZone:(struct _NSZone *)zone{
//懒加载

    if (singleton==nil) {

        singleton=[super allocWithZone:zone];

    }

    return singleton;

}

//单例方法 复制

-(id)copyWithZone:(NSZone *)zone{

    return self;

}

@end